Kodi doesn't use hardware acceleration. Software-decoder uses CPU resources too much and video playback is not smooth

If you use the 'odroid' built in account, Kodi uses the hardware acceleration.
But if you use an account that you have created, hardware acceleration WILL NOT WORK.

The problem is that to be able to run Kodi with hardware acceleration, you must use an account member of the 'video' and 'audio' groups (and probably many other groups).

So, if you use a different account and want hardware acceleration in Kodi you must run something like:

  usermod -a -G audio,video,users,plugdev,netdev <USERNAME>

where <USERNAME> is your user login name.

Credit: A forum user “apace” made this guide.